This application relates to semiconductor III-V alloy DH and SCH structures and to a method of preparing such structures for use in mid-infrared lasers.
The growth of semiconductor III-V compounds by chemical vapor deposition (CVD) using organometallics and hydrides as elemental sources for use in lasers has recently developed into a viable process. Further, the development of high power midwavelength infrared (MWIR) laser has been an active area of research for applications in military counter systems, high-resolution molecular spectroscopy, remote sensing of chemical and biological agents, and optical fiber communication. High power operation is of great importance to most of these applications as it enhances sensitivity and the spatial range of operation. At present, several semiconductor material systems grown by either liquid phase epitaxy or molecular beam epitaxy are being investigated to produce MWIR lasers. The metallo-organic chemical vapor deposition (MOCVD) process, based on the pyrolysis of alkyls of group-III elements in an atmosphere of the hydrides of group-V elements, is also a common growth technique because it is well adapted to the growth of submicron layers and heterostructures.
Open-tube flow systems may be used at atmospheric or reduced pressures in the MOCVD technique in producing the III-V alloys. The process requires only one high-temperature zone for the in situ formation and growth of the semiconductor compound directly on a heated substrate. Low pressure (LP-) MOCVD growth method offers an improved thickness uniformity and compositional homogeneity, reduction of autodoping, reduction of parasitic decomposition in the gas phase, and allows the growth of high-quality material over a large surface area. The LP-MOCVD technique has been successfully used to grow. In AsSbP alloys, which are potentially useful materials both for heterojunction microwave and optoelectronic device applications can be grown by liquid-phase epitaxy (LPE), molecular-beam epitaxy (MBE), conventional vapor-phase epitaxy (VPE), as well as MOCVD and MOMBE.
The molecular beam epitaxy (MBE) process involves the reaction of one or more thermal beams of atoms and molecules of the III-VB elements with a crystalline substrate surface held at a suitable temperature under ultra-high-vacuum (UHV) conditions. Since MBE is essentially a UHV evaporation techniques, the growth process can be controlled in situ by the use of equipment such as a pressure gauge, mass spectrometer and electron diffraction facility located inside the MBE reactor. The MBE growth chamber can contain other components for surface analytical techniques, including reflection high-energy electron diffraction (RHEED), X-ray photoelectron spectroscopy (XPS), low-energy election diffraction (LEED), electron spectroscopy for chemical analysis (ESCA), secondary-ion mass spectroscopy (SIMS) and ellipsometry, which can all be used as in situ surface diagnostic techniques during MBE growth, due to the UHV growth conditions.
MBE is an excellent crystal growth technology, especially for GaAs-based multilayer structures, because of its extremely precise control over layer thickness and doping profile, and the high uniformity of the epitaxial layer over a large area of a substrate ( greater than 3 inch diameter).
An object, therefore, of the invention is the preparation of a MWIR laser.
A further object of the subject invention is an III-V semiconductor providing a high power operation in a laser.
These and other objects are attained by the subject invention wherein a MWIR laser detector, transistor, or waveguide is made possible by the growth of a Double Heterostructure by MOCVD, MBE or a combination of the two growth techniques. A first Double Heterostructure is prepared as InAsSb/InAsSbP/InAs, and then the p-cladding layer is substituted with AlAs0.01Sb0.84.
Epilayers in III-V semiconductor lasers of the subject invention may be etched for mesa formation by first etching in a strong acid solution, such as a 10% hydrofluoric solution. Mesas are formed with standard photolithography procedures. A second step of immersion in a second solution of H2SO4,H2O2,H2O(1:1:20) is then conducted for 2-7 seconds at room temperature. The result is a smoother and more uniform temperature to etch approximately 0.1 xcexcm of the cap layer. The substrate is mechanically lapped and polished and contacts are formed.